Electromagnetism

Magnetic fields, forces on currents and charges, electromagnetic induction, and transformers.

Spec Points Covered
  • I can describe the magnetic field patterns around a long straight wire, a flat coil, and a solenoid.
  • I can use F = $BIL\sin\theta$ for the force on a currentThe rate of flow of chargeA property of matter that causes it to experience a force in an electromagnetic field. Measured in coulombs (C).. Measured in amperes (A).-carrying conductor.
  • I can use F = $BQv\sin\theta$ for the force on a moving charged particle.
  • I can explain why a charged particle moves in a circle in a uniform magnetic field and derive r = $\frac{mv}{BQ}$.
  • I can define magnetic fluxThe product of magnetic flux densityMass per unit volume of a material. Measured in kg m⁻³. and the area perpendicular to the field. Measured in weberThe SI unit of magnetic flux. One weber is the flux through an area of 1 m² when the magnetic flux density is 1 T perpendicular to the area. (Wb). and $use \Phi =$ $BA\cos\theta.$
  • I can define magnetic fluxThe product of magnetic flux densityMass per unit volume of a material. Measured in kg m⁻³. and the area perpendicular to the field. Measured in weberThe SI unit of magnetic flux. One weber is the flux through an area of 1 m² when the magnetic flux density is 1 T perpendicular to the area. (Wb). linkage and explain its significance for induction.
  • I can state and apply Faraday's law of electromagnetic inductionThe generation of an EMFElectromotive force. The energy transferred per unit charge by a source in driving charge around a complete circuit. Measured in volts (V). (and hence currentThe rate of flow of chargeA property of matter that causes it to experience a force in an electromagnetic field. Measured in coulombs (C).. Measured in amperes (A). in a closed circuit) when the magnetic fluxThe product of magnetic flux densityMass per unit volume of a material. Measured in kg m⁻³. and the area perpendicular to the field. Measured in weberThe SI unit of magnetic flux. One weber is the flux through an area of 1 m² when the magnetic flux density is 1 T perpendicular to the area. (Wb). linkage through a conductor changes..
  • I can state Lenz's law and explain how it is a consequence of conservation of energyThe capacity to do work. Measured in joules (J).Energy cannot be created or destroyed, only transferred from one form to another. The total energyThe capacity to do work. Measured in joules (J). of a closed system remains constant..
  • I can derive and apply the transformer equation and explain energyThe capacity to do work. Measured in joules (J). losses in real transformers.
  • I can explain the operation of a simple a.c. generator using flux linkageThe product of magnetic flux and the number of turns of a coil. Measured in weber-turns (Wb turns). changes.
  • I can use Fleming's left-hand rule for the motor effect and Fleming's right-hand rule for the dynamo effect.
  • I can describe practical applications including velocityThe rate of change of displacement. A vector quantity. Measured in m s⁻¹. selectors and cyclotrons.
Notes
01 Magnetic flux density (B) Magnetic flux density (B) → 02 Maximum force when the conductor is perpendicular to the field (θ = 90°, sin $\theta = 1)$ $F = BIL\sin\theta$ → 03 This is derived from $F = BIL$ by substituting $I = Q/t$ and $L = vt$ $F = BQv\sin\theta$ → 04 A charged particle entering a uniform magnetic field at right angles moves in a circle because $r = \frac{mv}{BQ}$ → 05 Magnetic flux (Φ) Magnetic flux (Φ) → 06 Faraday's law Faraday's law → 07 A transformer consists of two coils (primary and secondary) wound on a shared soft iron core $\frac{V_s}{V_p} = \frac{N_s}{N_p}$ → 08 Force on a wire → 09 Charged particle radius →
Σ Key Equations Full Reference →
On Data Sheet
Not on Data Sheet
$$F = BIL\sin\theta$$
$$F = BQv\sin\theta$$
$$\Phi = BA\cos\theta$$
$$\varepsilon = -\frac{d(N\Phi)}{dt}$$
$$\frac{V_s}{V_p} = \frac{N_s}{N_p}$$
$$r = \frac{mv}{BQ}$$